1. Field of the Invention
The present invention relates generally to a vehicular collision detection apparatus that detects collision of an object, such as a pedestrian, with a vehicle bumper.
2. Description of Related Art
Recently, there has been suggested a technique that includes an obstacle determination device mounted on a vehicle bumper member for the purpose of protecting a pedestrian. In the above technique, when the vehicle collision occurs, it is determined whether the collision object is a pedestrian. If it is determined that the object is the pedestrian, a protection device for protecting the pedestrian (for example, an active hood, a air bag on a cowling) is activated. An actual use of the above technique has been also studied.
In other words, in a case, where the protection apparatus (for example, the active hood) mounted on a hood is activated when the collision obstacle is not the pedestrian, various adverse influences may occur disadvantageously. For example, if the collision with a light-weighted fallen object, such as a traffic cone and a construction signboard, is not distinguished from the collision with the pedestrian, the protection apparatus may be uselessly activated, thereby generating unnecessary repair expenses. Also, in a case, where the collision with a heavy-weight fixed object, such as a concrete wall, a vehicle, is not distinguished from the collision with the pedestrian, the hood may be displaced backward while the hood is lifted, and thereby the hood may enter into a passenger compartment. Thus, the hood may damage the occupant. As above, because it has become required to accurately determine whether the obstacle is a pedestrian, there is proposed a conventional vehicular collision detection apparatus that includes a chamber member provided in a vehicle bumper at a front side of a bumper reinforcement. In the above configuration, the vehicular collision detection apparatus uses a pressure sensor for sensing a change of pressure in a chamber space in order to detect the collision of an object, such as a pedestrian, with the vehicle bumper (see, for example, WO 2005/098384 corresponding to US 2007-0181359, JP-A-2006-117157 corresponding to US2006-0087417).
However, in the above vehicular collision detection apparatus, in a case, where multiple pedestrians simultaneously collide with the vehicle or where the pedestrian and another object other than the pedestrian (for example, a utility pole, a garden tree) simultaneously collide with the vehicle, the collision of the pedestrian may not be accurately detected. For example, there may be occasions, where the utility pole collides with a part of the chamber member located between the pressure sensor and the pedestrian, and thereby the chamber member may completely collapse due to the collision with the utility pole. In the above occasions, the communication of air in the chamber member between the pressure sensor and the pedestrian may be disabled. As a result, the change of pressure due to the pedestrian collision is not transmitted to the pressure sensor, and thereby the collision of the pedestrian may not be detected disadvantageously.